It is well established that teacher-student interactive talk is critically important in supporting students to reason and learn in science. Teachers’ discursive moves in responding to student input are keys to developing and supporting a rich vein of interactive discussion. While initiation-response-evaluation (IRE) sequences have been shown to dominate science classroom discourse patterns worldwide, teacher ‘prompts’ are important for opening up opportunities for reasoning and higher level learning. This paper describes the analysis of video sequences for five expert elementary teachers across three countries to develop a coding scheme for these teachers’ ‘discursive moves’ to guide and respond to student inputs, that unpacks more completely the strategies they use to develop interactive discussion. The analysis showed varied patterns of knowledge transaction, with teacher discursive moves serving three broad purposes: to elicit and acknowledge student responses, to clarify and to extend student ideas. The patterns of talk were also related to the dialogic-authoritative distinction in analysis of talk, to show that this distinction is only clear for particular types of expert practice. While the particular moves teachers use vary across parts of lessons we argue that they are revealing of teachers’ particular beliefs and of systemic constraints, and that there exist patterns in the use of the discursive categories that capture how expert teachers build deeper level knowledge in classroom interactive talk. We describe ways in which the analysis can inform science teacher education and the professional learning of teachers of science.